Today's enterprise data centers store ever larger amounts of business critical data that must be immediately available and highly reliable. The data is also backed up or archived in large volumes and accessed periodically. To achieve reliability and performance goals for critical data, it is preferable to employ dual ported disk drives such as Fibre Channel or SAS (Serial Attached SCSI) drives in a highly available storage system that employs multiple storage processors or controllers, as this architecture provides the highest performance and reliability. But single ported disk drives, such as SATA (Serial Advanced Technology Attachment) drives, are less costly and provide greater capacity, making them ideal for online storage of backup or archived data. It is desirable for a storage system to be able to support either type of drive—dual or single ported—so that the user's system can be customized to optimize storage performance, capacity, reliability, and cost, as the user's applications require.
To date, in order to employ single ported drives such as SATA drives in a highly available storage system employing multiple storage processors or controllers, 2:1 multiplexers or switches have been employed as interfaces between the single SATA port and the multiple controllers. But it is difficult to integrate both types of drives—single and dual ported—into a single system without increasing software and hardware complexity. What is needed is a device for interfacing either single or dual ported drives to multiple storage processors or controllers without adding system complexity.